1. Field of the Invention
The present invention relates to a device for making split bearing assemblies in connecting rods, in particular by cracking a continuous bearing housing into two parts to provide a properly fitting bearing cap during manufacture of the connecting rods.
2. Description of Prior Art
A recent development in manufacturing connecting rods is to forge the rod in one piece including a one piece annular bearing housing having a central bore for the connection to a crank shaft journal, and then exerting a force from the interior of the bore to crack the continuous bearing housing into two sections to form a bearing cap so that the rod can be installed on a crankshaft journal. When properly broken, the two parts of the bearing housing will fit back together exactly as they separated with only a slight distortion of the bore. The cap can then be bolted in place and the bore honed to its final dimension. The internal bore in the continuous bearing housing is generally notched at diametrically opposed positions where the crack is to take place to insure that the breaks will be along a diametrical line. High speed, reliable and repeatable production is important in order to keep manufacturing costs low.
At the present time, a typical system for breaking the bearing housings for connection rods is shown in U.S. Pat. No. 4,569,109. The overall process is explained in that patent. In that device, a typical wedge system is used for breaking the bearing housing, wherein a wedge is placed between two dies that separate as the wedge is driven into place. The dies exert forces generally perpendicular to a bisecting plane lying along the axis of the bore. However, wedges will tend to create bending moments in the members forming the bore, and there is friction which makes it difficult to control the load applied to the part. The friction can cause the wedges to tend to weld themselves together. The wedges fail to provide uniform forces, causing problems in manufacture, such as distortions, and incorrectly cracked bearing housings. Thus the scrap rate is relatively high, and the process is slow, and not easily controlled.